1. Field of the Invention
The present invention relates to a single-shaft shifting mechanism for change-gear transmissions of the type wherein selected gear ratios are engaged and disengaged by axially movable gears or axially movable jaw clutch members. In particular, the present invention relates to an improved single-shaft shifting mechanism assembly employing an improved shift-block-to-shift-shaft mounting structure.
2. Description of the Prior Art
Single-shaft shifting mechanisms for shifting multiple-speed vehicular transmissions are well known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,621,537 and 4,920,815, the disclosures of which are incorporated herein by reference. These mechanisms, in certain situations, are improvements over multiple parallel shift rail devices (see U.S. Pat. Nos. 4,445,393 and 4,722,237, the disclosures of which are incorporated herein by reference), as they may require fewer parts, require less space, be more economical to produce and/or allow improved transmission control.
The prior art single-shaft shifting mechanism assemblies were subject to improvement, as, under certain conditions, the shift block might tend to move relative to the shift shaft, which could cause an undesirable "notchy" feeling when shifting the transmission and a loss of critical alignments and/or could eventually lead to failure of the shift-block-to-shift-shaft attachment.
In the prior art single-shaft shifting mechanisms, the shift shaft was provided with a flat surface which mated with a flat surface on the bottom or inner diameter surface of the shift block, and the flat surfaces were secured by a cap screw or like fastener. As a result of inherent tolerances in manufacturing, when the block-to-shaft joint loosened due to loading during shifting, the block did not fit tightly on the shaft, which resulted in a loss of accurate alignments and caused a notchy feeling when shifting. Further, the loosening also allowed the forces imparted to the shift block to be translated primarily into side loading of the retaining fastener, which, if allowed to continue, may eventually lead to failure of the fastener under fatigue cycling.